Mapping Hacks

Why You Can’t Watch Broadcast TV #18

Chapter 2, Mapping Your Neighborhood

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Reading "delimited_file"... 25%... 50%... 75%... Done!

Writing "37:38:122:123.sdf"... Done!

Removing temp files...

Done!

SPLAT! should create a bunch of files in the same directory with filena-

mes like 36:37:120:121.sdf. The numbers in the filename correspond to

the latitude and longitude of the edges of the original DEM file. If these

files are going to live in a different directory than the one you’re running

SPLAT! from, you need to put that directory path on a single line in a file

called .splat_path in your home directory.

SPLAT! uses the Longley-Rice Irregular Terrain Model to estimate how radio

frequencies travel. The model needs some parameters to describe atmo-

spheric conditions that affect how radio waves travel. SPLAT! provides sen-

sible defaults in a file called sample.lrp. Copy this file from the splat-1.1.0/

source directory into your current directory, and rename it splat.lrp. Here’s a

snippet from the beginning of the file:

15.000 ; Earth Dielectric Constant (Relative permittivity)

0.005 ; Earth Conductivity (Siemens per meter)

301.000 ; Atmospheric Bending Constant (N-units)

300.000 ; Frequency in MHz (20 MHz to 20 GHz)

5 ; Radio Climate (5 = Continental Temperate)

0 ; Polarization (0 = Horizontal, 1 = Vertical)

0.5 ; ...